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Circumference estimate

Free body fat calculator

Take a few tape measurements to estimate body-fat percentage, fat mass and fat-free mass without creating an account.

Free, no credit card General estimate, not medical advice.
Tool available

Measure your body composition

For adults. Measure without compressing the skin and repeat under similar conditions; a few centimetres can move the result.

Sex used by the equation
The circumference method uses two biological equations; this choice does not describe gender identity.
Method and assumptions

Method and assumptions

The Hodgdon–Beckett circumference method estimates body density from logarithms of height and circumference differences, then converts it to body-fat percentage.

The male equation uses height, abdomen and neck. The female equation adds hips. All measurements are converted to centimetres before calculation.

Fat mass and fat-free mass are then derived from entered body weight; they are not direct measurements.

Important limitations

Important limitations

  • Tape placement or tension errors can materially change the estimate.
  • A population equation can be less accurate for some body shapes, ages and muscularity levels.
  • This result is not a diagnosis or a clinical body-composition scan such as DEXA.
2026-07-26

Sources and method

  1. U.S. Army Medical Department — Hodgdon–Beckett equations, table 13-5
  2. NCBI Bookshelf — Body-composition methods and Naval Health Research Center reports
FAQ

Frequently asked questions

How should I measure the abdomen?

Keep a flexible tape horizontal without compressing the skin, and repeat the same measurement site each time. Consistency is essential.

Why are hips only used in one equation?

The method publishes sex-specific equations; the female equation uses abdomen plus hips minus neck.

Does this replace a DEXA scan?

No. It is a repeatable tape-measure estimate, not a direct clinical analysis of body composition.